Rory McIlroy among top golfers struggling through treacherous Oakmont rough in opening round of US Open

Rory McIlroy among top golfers struggling through treacherous Oakmont rough in opening round of US Open

McIlroy's promising front nine unravels with sequence of bogeys in difficult playing conditions

Rory McIlroy hits his shot on the 17th hole during the first round of the U.S. Open. (Bill Streicher-Imagn Images)

Rory McIlroy plays a shot from a bunker on the 17th hole during the U.S. Open. (Bill Streicher-Imagn Images)

Rory McIlroy walks off the first tee during the first round of the U.S. Open. (Charles LeClaire-Imagn Images)